Beam position control for an extreme ultraviolet light source

Abstract

A system for an extreme ultraviolet light source includes one or more optical elements positioned to receive a reflected amplified light beam and to direct the reflected amplified light beam into first, second, and third channels, the reflected amplified light beam including a reflection of at least a portion of an irradiating amplified light beam that interacts with a target material; a first sensor that senses light from the first channel; a second sensor that senses light from the second channel and the third channel, the second sensor having a lower acquisition rate than the first sensor; and an electronic processor coupled to a computer-readable storage medium, the medium storing instructions that, when executed, cause the processor to: receive data from the first sensor and the second sensor, and determine, based on the received data, a location of the irradiating amplified light beam relative to the target material in more than one dimension.

What is claimed is: 
     
       1. A method of aligning an irradiating amplified light beam relative to a target material, the method comprising:
 accessing first, second, and third measurements of a reflected amplified light beam, the first measurement obtained from a first sensor, the second and third measurements obtained from a second sensor having a lower acquisition rate than the first sensor, and the reflected amplified light beam being a reflection of the irradiating amplified light beam from a target material, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted to a plasma; 
 determining, based on the first measurement, a first location of the amplified light beam relative to the target material in a direction that is perpendicular to the direction of propagation of the irradiating amplified light beam; 
 determining, based on the second measurement, a second location of the amplified light beam relative to the target material in a direction that is perpendicular to the direction of propagation of the irradiating amplified light beam; 
 determining, based on the third measurement, a location of a focal plane of the amplified light beam relative to the target material in a direction that is parallel to the direction of propagation of the irradiating amplified light beam; and 
 repositioning the irradiating amplified light beam to relative to the target material based on one or more of the first location, the second location, or the location of the focal plane to align the irradiating amplified light beam relative to the target material. 
 
     
     
       2. The method of  claim 1 , further comprising determining an adjustment to the location of the focal plane of the amplified light beam based on the determined location of the focal plane, and wherein repositioning the irradiating amplified light beam comprises moving the focal plane of the irradiating amplified light beam based on the determined adjustment to the location of the focal plane. 
     
     
       3. The method of  claim 1 , further comprising determining an adjustment to the amplified light beam based on one or more of the determined first location or the determined second location. 
     
     
       4. The method of  claim 3 , wherein:
 the amplified light beam comprises a pulse of light, 
 the determined first location comprises a location of the amplified light beam relative to the target material in a direction parallel to a direction in which the target material travels, and 
 the determined adjustment to the alignment to the amplified light beam comprises a distance between the amplified light beam and the target material in the direction parallel to the direction in which the target material travels, and 
 repositioning the irradiating amplified light beam comprises causing a delay in the amplified light beam that corresponds to the distance between the amplified light beam and the target material such that a subsequent pulse of light intersects a target material. 
 
     
     
       5. The method of  claim 3 , wherein:
 the determined second location comprises a location of the amplified light beam in a direction that is perpendicular to the direction in which the target material travels and perpendicular to a direction of propagation of the amplified light beam, and 
 the determined adjustment to the alignment of the amplified light beam comprises a distance between the amplified light beam and the target material location, and 
 repositioning the irradiating amplified light beam comprises:
 generating an output based on the determined adjustment, the output being sufficient to cause repositioning of an optical assembly that steers the amplified light beam; and 
 providing the output to the optical assembly. 
 
 
     
     
       6. The method of  claim 3 , further comprising determining an adjustment to the location of the focal plane of the amplified light beam based on the determined location of the focal plane. 
     
     
       7. The method of  claim 6 , wherein repositioning the irradiating amplified light beam comprises:
 generating an output based on the determined adjustment to the location of the focal plane, the output being sufficient to cause repositioning of an optical element that focuses the amplified light beam; and 
 providing the output to an optical assembly that comprises the optical element. 
 
     
     
       8. The method of  claim 1 , wherein the third measurement comprises an image of the reflected amplified light beam, and determining a location of the focal plane of the amplified light beam comprises analyzing the image to determine a shape of the reflected amplified light beam. 
     
     
       9. The method of  claim 8 , wherein analyzing the image to determine a shape of the reflected amplified light beam comprises determining an ellipticity of the reflected amplified light beam. 
     
     
       10. The method of  claim 1 , wherein:
 the third measurement comprises images of the reflected amplified light beam sampled at multiple locations, and 
 determining a location of the focal plane of the amplified light beam comprises comparing the widths of the reflected amplified light beam at two or more of the multiple locations.